The conversion of synthesis gas via Fischer-Tropsch catalysts is a well known process. Such catalysts generally produce liquid products which include components such as organic acids, aldehydes, alcohols and olefins which are undesirable for use as fuels. It is also known to employ zeolite catalysts for the conversion of various organic compounds. For example, U.S. Pat. Nos. 4,276,438 and 4,278,827 disclose processes for the conversion of aromatic compounds to dialkylbenzene compounds. Each process requires a particular type of a zeolite catalyst which has been modified with either a Group IB or a Group IVB metal.
U.S. Pat. No. 3,775,501 discloses a process for the production of aromatics from hydrocarbons and air over a zeolite catalyst. U.S. Pat. No. 3,271,418 discloses a process for cracking petroleum gas oil to produce high octane gasoline over a zeolite catalyst where the original alkali metal has been replaced by other cations.
Others have disclosed the use of Fischer-Tropsch catalysts with zeolites in organic synthesis. U.S. Pat. No. 4,279,830, for instance, discloses a two reactor process for converting synthesis gas to oxygenates and hydrocarbons by reducing CO in the first reactor over a Fischer-Tropsch catalyst, where a zeolite is optionally present, followed by treatment in the second reactor over a zeolite catalyst.
U.S. Pat. No. 4,269,783 discloses a process for the conversion of synthesis gases to hydrocarbon mixtures such as olefinic naphtha with an aromatic content of less than 20 weight percent. The olefin plus aromatic content of such products comprises at least 50 weight percent. The zeolite component of the catalyst combination comprises not more than 0.5 weight percent alkali metal.
Lastly, U.S. Pat. No. 4,086,262 discloses a method for the conversion of synthesis gas to hydrocarbon mixtures rich in aromatics. A heterogeneous catalyst comprising zeolites and Fischer-Tropsch synthesis catalysts is employed.
Thus, while the art provides catalysts and processes for the conversion of synthesis gases and other organic feedstocks to various hydrocarbons over mixtures of zeolite and Fischer-Tropsch catalysts, it has not disclosed the specific production of saturated gaseous hydrocarbons.